Geologic map of the Keg Mtn. Ranch quadrangle, Juab County, Utah (MP 99-5)

By: M. A. Shubat, T. J. Felger, and J. K. King

The Keg Mtn. Ranch 7.5 minute quadrangle is in west-central Utah and includes the eastern part of Keg Mountain. The oldest rocks exposed in the quadrangle are Cambrian quartzite and limestone. These rocks were deformed during the Sevier orogeny, which produced thrust faults and folds that are exposed in adjacent quadrangles. Most of the quadrangle is underlain by Tertiary volcanic and intrusive rocks. Several calderas and cauldrons are in and near the Keg Mtn. Ranch quadrangle; they are part of a large, late Eocene to early Oligocene igneous center that spans the Thomas Range, Keg Mountain, and northern Drum Mountains. The major volcanic units of this age in the quadrangle are, from oldest to youngest: the Keg Tuff; Mt. Laird Tuff; Joy Tuff; and Dell Tuff. Late Miocene rhyolite of Keg Mountain and Topaz Mountain Rhyolite were erupted from scattered local vents. Lake Bonneville covered much of the quadrangle during the late Pleistocene and produced most of the surficial deposits. The lake left distinctive sediments and landforms, including marl, V-bars of the Snow Plow, and prominent Bonneville and Provo shorelines. Other surficial deposits include stream alluvium, colluvium, and several generations of alluvial fan deposits. Potential mineral resources in the quadrangle include gold, sand and gravel, cement rock, high-calcium limestone, zeolites, crushed stone, and dimension stone.

Other Information:
Published: 2000
Pages: 22 p.
Plates: 2 pl.
Scale: 1:24,000
Location: Juab County
Media Type: Paper Map